Chess960 tactic on a5 (c3)
c9-09598naming tag (square·N)Opens in the app if installed, otherwise downloads the APK.
The tactical motive
Chess960 twist: use the unusual starting setup of the pieces.
Mate: a forcing sequence that ends the game — the king has no escape.
Mate in 4: a forced checkmate in four moves — every reply is covered.
Difficulty 2250 ShuffleRating — expert level — few solve it at first try.
White to move — find the best continuation
How to recognize this tactic
In Chess960 the pieces start on unfamiliar squares, so tactics appear earlier and from unusual angles. Do not trust classical patterns — read the actual lines of the bishops, the rooks and the queen from where they really stand in this position.
This is a forced mating attack. Start from the enemy king: which of its squares are already covered, and which move takes away the rest while keeping the king in check? Forcing moves — checks and captures — are what turn an attack into mate.
A mate in four is a longer forced net: each of your moves is a check or an irresistible threat, and the king is driven step by step to a square where it is finally trapped. Verify that the defender has exactly one reply at every branch.
General method: before you move, list the forcing candidates — every check, every capture, every direct threat — and calculate those first. The solution to a tactic is almost always among them.
Position on the board
White: king c1, queen c3, rook e1 e6, pawn c2 f3 g4 c5 h5.
Black: king a8, queen d5, pawn a4 a5 g5 h6 c7.
9 white and 7 black pieces are on the board; the puzzle position arises after move 36.
The position in numbers
White are ahead by 10 points of material (24 against 14; pawn = 1, knight and bishop = 3, rook = 5, queen = 9) — the tactic has to convert or outweigh that.
The white king stands on c1, the black king on a8.
It is White to move on move 36, with 40 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 5 pawns, Black 5. Files fully open (no pawns of either colour): b, d, e — natural highways for the rooks and queen. Half-open for White: a.
The White king has 2 empty squares to step to right now — the fewer they are, the closer a mating net.
Solution & explanation
Main line
36. Qxa5+ Kb7 37. Qa6+ Kb8 38. Re8+ Qd8 39. Rxd8#
Why it works
- Best move. queen to a5 is exactly what the engine plays (#3).
- Spot on — queen to a6 (#2).
- Precise: rook to e8 is the top choice (#1).
- Best move. rook to d8 is exactly what the engine plays (#).
- The line ends in a forced mate in 4.
- If instead Kb7, then Qa6+ and you stay on top.
Move by move
- 36. Qxa5+ — queen to a5 (capture) with check
- Kb7 — king to b7
- 37. Qa6+ — queen to a6 with check
- Kb8 — king to b8
- 38. Re8+ — rook to e8 with check
- Qd8 — queen to d8
- 39. Rxd8# — rook to d8 (capture) and it is checkmate
Types in this puzzle
Mate in 4+
A long forced mating combination.
Mate in four or longer is a marathon of forcing moves where the grip must never loosen. The tools are the same: checks, double threats and sacrifices that deny the opponent a single free tempo. Do not juggle the whole tree at once — walk the main line all the way to mate first, then verify the side branches. If somewhere the defender finds one quiet move that holds, your very first move was wrong.
Win the pinned piece
The pinned piece cannot run — attack it again and win it.
A pinned piece cannot flee, which means you can win it outright by attacking it one more time. Count attackers against defenders: if you outnumber them, the piece is yours. The best extra attacker is a pawn, since it costs less than anything it might capture. Do not rush the capture — build up the pressure first, then harvest.
About this position
These pieces come from starting position #650.
SP-650 · BastionScout — The king starts one file off-centre, on c or f, and a knight begins in a corner.
The king starts on c1, the rooks on a1 and d1, the queen on g1.
The king already stands on c1, so castling long moves only the rook, from a1 to d1.
The bishops stand on e1 and f1; their long diagonals reach a5 and a6 once the d- and e-pawns step aside.
The pawn on b2, c2 is defended by the king alone — the same soft spot f2 is in the classical setup.
The setup belongs to the BastionScout family; read right to left it becomes position 213.
The engine's main line opens with d4, putting a pawn straight into the centre.
Morozov Balance Index: 43 of 100 — class C — noticeable edge. Engine evaluation of the starting position: +28 centipawns for White (depth 47, 400 000 000 nodes).
Explore position #650Provenance
Mined from the project's engine self-play games.
Pack 015 · SP-650
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